With the 2016 Olympics rapidly approaching, progress on one of host city Rio de Janeiro's most important infrastructure projects has slowed while its cost balloons, contributing to concerns about the city's preparations for the summer games, slated to start on August 5.

The opening of Line 4 of Rio's subway system, meant to move passengers from Ipanema beach to the Barra da Tijuca suburb where the Olympic Park and Village are located, has been repeatedly delayed, according to the Associated Press.

At present, officials say the subway line will be opened four days before the games kick off, a slim margin that leads many to worry about adequate testing of the new transport line.

"They are leaving so little time to try this massive system," Jose Manoel Ferreira Goncalves, president of FerroFrente, an organization of railway experts, told the AP. "What guarantee do we have that such a sensitive and complicated project is in order?"

The perilous conditions of Rio state's finances has added to worries about the city's ability to successfully host the games. Last week, Rio state's governor declared a "state of public calamity," decreeing that emergency measures were necessary to prevent "a total collapse in public security, health, education, transport and environmental management." (Though Rio de Janeiro's mayor has stressed that his city's finances are in good order and denied "that the Olympics broke the state of Rio.")

In recent years, Rio state benefited from plentiful oil reserves, but as the global oil slump wares on, the state has seen its wealth and ability to meet debt obligations diminished.

The state has missed payments to retirees and public workers (including police), and its failure to make loan payments has led the federal government to hold onto $284 million meant to pay for Olympics-related infrastructure projects, including subway Line 4.

And while Rio state auditors are looking into why Line 4's cost has spiked from $1.6 billion to $2.9 billion, federal police are investigating whether construction company Odebrecht bribed officials involved in Line 4's development.

Early on Tuesday, two members of Australia's Paralympic squad were robbed at gunpoint in a Rio park. "This is not an isolated incident, athletes have been mugged while training or competing in Rio test events and we want our athletes protected," Australia Olympic team leader Kitty Chiller said.

Just two days before that robbery, a group more than 20 men armed with assault rifles and grenades, attempting to free a suspected drug trafficker, stormed Hospital Souza Aguiar, one of the hospitals recommended by the city and the US embassy to treat tourists during the games.

The "carefully orchestrated attack" was successful but led to a shootout, leaving one person dead and two wounded. Officials have vowed not let the attack go unpunished, but for the police involved, the incident was a reminder of how tenuous the city's security situation is.

"People in our line of duty go through these kinds of different experiences," said Fabio Melo, a sergeant guarding the suspected drug trafficker, according to the AP. "But we are defenseless. I am defenseless, you are defenseless and the whole population, too."